Bootstrap Responsive Design Help

So, when I resize my window, the images (which will be links to portfolio items eventually) are fine until a certain point, where they seem to smush over each other, and then they stack. is there a way to solve this issue? I’m still trying to figure it out myself, but anyhelp would be greatly appreciated.

Here is a link to my pen - https://codepen.io/KaelanBlayde/full/WEyPNJ

Thank you so much, friends!

I ended up figuring it out. I used .thumbnail, which actually works better so I can caption the links. w3schools is a godsend.